If your piston looks like this, you haven't changed your rings since your 15 year old son was born! As a matter of fact, your silencer packing is blown, your using cheap oil and your air filter is full of mouse crap! Dude, You need to work on your bike once in a while.

Classic example of detonation. In layman?s terms, you overheated the dog out of your motor. This is caused by poor or no coolant, lean jetting, vacuum leaks, overly advanced timing, poor ignition components or insufficient piston clearance.

More detonation!

The scoring marks indicate insufficient piston clearance. Use the manufactures recommended specifications for clearance when changing your piston. It�s always better to go with a little more clearance than not enough

This is what happens when a piece of your valve, spark plug or lower end connecting rod bearing meets the top of your piston.

The arrow on the front of your piston points toward the front. Put it in backwards and you'll have something that looks like this. If you did this, you already know what your cylinder looks like.

No problems here. This is what the piston looks like when all is well.

Think about this. Your piston travels at speeds of about 125 mph and then comes to a complete stop! This would kill the average man at half that speed. Couple this with the fact that your engine does this up to 10,000 times in a single minute. That's some serious inertia! Throw some extra friction, poor maintenance or hack engine mods into the mix and you?ll get something that looks like this.

This is called a four point seizure. The engine was not warmed up before the ride. The engine may lock up for �no reason� and then start after cooling down for a few minutes. Give your engine a few minutes to warm up and you wont have this problem.